Method of and apparatus for coating paper



Nov. 1, 1938. D. R. MACDONALD I 2,135,405

METHOD AND APPARATUS FOR COATING PAPER Filed Sept. 15, 1956 2 Sheets-Sheet 1 Nov. 1,

D. R. MACDONALD METHOD OF AND APPARATUS FOR COATING PAPER 2 Sheets-Sheet 2 Filed Sept. 15, 1936 I ll IIIIHI M V ew r v w E NWM E m mwm Patented Nov. 1, 1938 2,135,406 V METHOD OF AND APPARATUS FOR COATING PAPER Donald R. Macdonald, Leominster, Mass. Application September 15, 1936, Serial No. 100,925

8 Claims.

This invention relates to an improvement in the method and apparatus for effecting an even distribution of coating materials to webs or sheets of paper or like materials.

-'- The'application of coating materials is usually accomplished by applying the desired material to a traveling ribbon, web or sheet of material by spraying the material onto the sheet, by immersing the sheet in a bath of the material, or

30 by bringing the sheet into contact with a roll or other device to which the coating material has been applied. The coating material thus applied is smoothed out to a uniform thickness, and the excess material removed by scrapers, brushes, air jets or other suitable mechanism.

My invention deals with an improved method of and apparatus for effecting a more even distribution of this coating film on the traveling web, and deals more particularly-with the im- 20 provement in the apparatus which employs a jet of air for the above purpose. a

In the manufacture of coated paper it is very. necessary that the coating materials be distributed uniformly over the entire width and length of the sheet or webin order that subsequent operations on this sheet or Web may be satisfactorily performed and a high grade of paper having a uniformly smooth and polished surface be obtained. If the coating material is notdeposited in the proper amount or of the proper thickness, or is deposited unevenly or. of thicker composition on some portions of the sheet than others such irregularities cause subsequent operating and manufacturing difficulties, and greatly; reduce the quality of thesheetfinally produced.-

One of the most satisfactorymeans found to eifect an even distribution of the coating mate rials over a traveling webof paper is toimpinge a narrow jet of compressed air (or other gas) on I 40 and against the sheet after the coating material has been applied. Thisjet of air (or gas) being directed uniformly overthe entire width of the traveling web or. sheet. The impact of the air on the freshly coated sheet accomplishes three nec,-

V a sufficient thickness or amount of coating applied; and third, it removes any surplus or unnecessary coating material from the sheet efiecting economy in cost and insuring a uniform v product.

While my invention is hereinafter described as dealing particularly with the application of coating materials to a traveling web or sheet of paper, and an improvement on the methods of and apparatus for distributing these coatingmaterials uniformly over the web or sheet by a jet of air,

still this description shall not be interpreted as limiting my invention to the application of coating materials exclusively to paper, or the application of my improvements exclusively to dis- Fig. 4 shows an enlarged view of a portion of Fig. 2.

Fig. 5 shows an enlarged view through one of the air adjusting valves.

Fig. 6 shows a modification of my device as applied to an air distributing nozzle and is'optional with, the device shown in Fig. 3.

Inmy preferred form of device the sheet or web of paper or other material is taken from a roll I over one or more guide rolls 2 and then over a coating roll 3 which roll is immersed in a I bath of coating mixture contained in tank 4.

The coating mixture in tank 4 is in fluid form and a coating or layer adheres to the surface'roll 3. This surface comes in contact with the under side of. the traveling web or sheet and leaves on the surface of the sheet a quantity of coating ma terialmore or less uniformly distributed over'its entire width.

After leaving roll 3 the uncoated side of the sheet passes around r0115 being drawn or moved along by means'of a porous belt 6 traveling over a suction box I and driven by means of rolls 8,

The suctionbox Tholds the sheet r web tightly against the porous belt 6 and results in sufficient friction between the paper web and the belt to draw the paper along with the belt over the variouscoating and guiding rolls previously referred to from the storage roll I.

Adjacent to roll 5 is mounted a compartment 'or box 9 of suitable size and shape extending the entire width of the machine and of the traveling web One side or corner 01' this box is provided with a narrow groove'or slot ll located adjacent to the roll 5. Compressed air or other gas is supplied through pipe I l to the interior of box 9 and the box and slot III are so located that this air or gas pressure will impingeon the surface of the traveling web passing over roll I. This web is designated as lw.

The box 9 is mounted in a manner so that it can be moved into suitable position and location relative to roll 5 and the traveling web I10 and can also be swung or moved out of position when necessary for examination or any other reason. I

The mechanism for accomplishing this purpose is not shown.

The mechanism heretofore described deals with a conventional method of applying a coating material to a traveling web of paper and illustrates particularly as before mentioned the air jet type of device for distributing this coating uniformly over the surface of web I10 and of removing any excess, surplus or unnecessary material.

Dealing more particularly with my invention,-

the coating roll I usually deposits more coating material on web iw than is necessary or desirable on the finished sheet. The removal of this excess material assists materially in accompllshing the first twoobjectives previously mentioned, namely, smoothing oil or leveling of any high or thick portions of the coating material, and filling in any thin portion or portions of the traveling web which were not sufiiciently covered. By having an excess of coating material these two objectives can be more readily accomplished'but nevertheless this excess coating material must be removed entirely away from the sheet and preferably delivered back to tank 4 for reuse. Any and all excess material which is removed from the sheet by the air jet is first collected in the ex pansion pans It and from which pans it can be removed for reuse.

In removing this excess material from the web lw by any of the present methods, and particu-- larly with the air jet method, it is diificult'to get the removed material completely away from the parts of the machine adjacent to the roll I and a the traveling web Ito, and particularly away from parts immediately adjacent to the air jet opening II.

The velocity of air from jet i. which smooths and removes the excess coating material is relatively high and this velocity tends to break up the liquid of the coating material into more or less fine drops of vapor, which in turn being suspended in the air from the jet travel with this air .until its velocity is very much dispersed.- The purpose of the expansion pans i3 and I4 is to provide space where this air 'velocity can be reduced. and the excess coating material traveling with the air allowed to drop into the pans. However, the allowable space for these pans is limited and there is a tendency for the air to follow the edge of the pan downward toward the roll 5 and back upwards arid under the box 9 resulting in precipitatlon of coating material on theunder side at point I! said precipitated material gradually increasing in mass toward the roll 5 over which the coated paper is passing.

Thismassofpartiallysolidifiedcoatlngmaterial which lodges on the bottom of box 0 is not uniform but projects more or less at scattered points until the mass may be increased to an extent where it partially or wholly obstructs the jet of air coming from the jet or nozzle ll, under whicheondiflonanexcessof coatingmaterialis leftonthe sheet at that point. This mass of deposited coating material thus deposited along the bottom of box 0 may be built up until it actually touches the traveling sheet, and scraping ofl the coating material causes a deficiency of coating at that point and a' thin streak or mark lengthwise of the web. I

I have found a method whereby not only is there a minimum of coating material deposited on the bottom of the box 9, but such material as may come in contact with the box is immediately removed before it can build up to cause trouble.

To accomplish my purpose I provide an auxiliary air jet ii located on the bottom of box 9. My preferred form of construction is to provide on the bottom of box I a plate l8. On the upper side of and between the plate l6 and the box 9 is a. distributing air chamber l8. Connecting to this air chamber I. are a plurality of openings or holes ,II which connect with the interior of box I and aresupplied with air pressure from the interior of this box furnished through pipe ll. The.,air which is under pressure in the interior of box I passes through openings or holes is into the distribution chamber IO and from this chamber through a narrow slot or opening l5 which distributes this air under pressure on the under surface of box I and directly across that portion of I! where the coating material tends to accumulate.

In order to effect a uniform and also an ad position on the under side of box'il.

By properly proportioning the amount of air and size of opening II, the eddy currents of air caused by the impinging of air through slot l0 against the web lw on roll I can be largely eliminated or removed insofar as this eddy current of air tends to carry the coating material back up and onto the under side of box 8 at point it.

By providing this auxiliary air jet Ii directly along under surface of box 9 I not only prevent any accumulation of coating material on any portion of the box and particularly at point 12 but assist in the operation oi air through distributing slot II by eliminating eddy currents below this slot and electing a more thorough and uniform removal of any. surplus coating material on the web lw.

The valves I! not only serve .to adjust the distribution of the air at various points in the width of the web but also toadjust the amount of air to be in proper proportion or ratio with the air impinged on the sheet through slot l0.

- As anoptional method of supplying this auxiliary air jet to the under surface of box 9 I may provide a slotted pipe or tube as illustrated in Fig. '8. This shows a pipe 20 with a slot or openlng'il extending the entire width of the under surface of the box 0. To this pipe 20 is supplied air under pressure controlled by valve 22. This valve 22 serves to properly proportion .the amount of air delivered through slot II and My invention however, is not limited to either of the particular arrangements illustrated in Figs. 3 and 6 or to the specific use of a primary air jet for distributing uniformly a coating material over a web or sheet or this means for removing surplus material.

The foregoing description and illustrations used therewith is simply illustrative of my preierred method of application and apparatus therefor.

Having described my invention, what I desire to claim by Letters Patent, is:

1. An apparatus for coating paper comprising means for applying a coating material to a traveling web, gas blast means for smoothing said applied material and eilecting a removal of any surplus material, and auxiliary gas blast means for effecting complete removal of any surplus coating material deposited on said first mentioned gas blast means.

2. An apparatus for coating paper, comprising means for moving a web of paper, means for applying a coating to said moving web, means for impinging a jet of air under pressure on said moving weband the coating thereon and gas blast means for preventing surplus coating material removed from the traveling web by air pressure from accumulating on parts of said jet impinging means adjacent to said traveling web.

3. An apparatus for coating paper comprising a means for applying a fluid coating to a moving web, means comprising an air jet for distributing said coating over said web and means comprising an auxiliary air jet operating in conjunction with the first mentioned jet for eflfect ing more even distribution 01' the coating material on the web and an effective removal of the 'surplus coating material deposited on said first mentioned air jet means.

4. An apparatus for coating paper comprising means for applying a fluid coating to a moving web, gas blast means for distributing said coating over the surface of the moving web, means operating in conjunction with the before mentioned distributing means for eli'ecting a more even distribution of the coating material on the web and a more eii'ective removal of the surplus coating material from adjacent parts 01' said first -mentioned distributing means and means for adjusting its eflective action.

5. 'An apparatus for coating a traveling web,

comprising means for applying a coating to said comprising an auxiliary jet operating in con junction with said first mentioned air jet for efiecting a more even distribution of the coating material on 'the web, and a more eifectiveremoval of the surplus coating material, and means for adjusting the efiective action of the auxiliary air jet relative to the first mentioned air jet.

6. The method of coating paper comprising the application of a coating material in fluid suspension to a moving web, the subjection of said moving coated web to a jet of air for effecting smoothing of the coating material and partial removal of any surplus coating material, and the subjection of said moving coated web and adjacent parts to a second jet of air for completing the removal of said surplus coating material from adjacent parts from which it may be redeposited back on the'web.

"I. An apparatus for coating paper comprising means for applying a coating material to a traveling web, means for impinging a jet of air on said moving web to smooth said applied material and effect a partial removal of surplus material, and auxiliary means for impinging a second jet 01 air on said moving webto complete the removal of surplus coating material already partially removed by said first jet, said auxiliary means including a nozzle positioned to direct its jet of air across portions of the apparatus adjacent the traveling web, whereby to maintain said portions tree of accumulation of coating material.

8. An apparatus for coating paper comprising means for applying a coating material to a traveling web, means for smoothing said applied material and eiiecting a partial removal of surplus material from said web, auxiliary means for efiecting complete removal of any surplus coating material already partially removed by said smoothing means, and deposited on said smoothing means, and means for adjusting said auxiliary means relative to said smoothing means.

DONALD R. MACDONALD. 

